Sampson, Edward G., author
John Wiley & Sons, 1976
Buku Teks
Fowler, Peter J., author
Routledge, 1995
Buku Teks
edited by I. William Zartman and William Mark Habeeb
Westerview Press, 1993
Buku Teks
Holt, Rinehart and Winston, 1985
Buku Teks
Hamner, Tommie
Prentice-Hall, 1990
Buku Teks